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H; A. WOOFTER.

TRANSFORMER SECONDARY CONNECTION FOR ELECTRIC METAL WORKING APPARATUS.

, APPLICATION FILED JULY 30,1920. 1,375,765,

Patented Apr. 26, 1921.

1 gwue/wcoz f/er r a. Z00 ofzr. W /1 l5 5 rarest HERBERT ADDISON VJOOFTER, 0Z3 SW'AIHPSCOTT, MASFQACHUSETTS, ASSTGNOR TO THOMSON ELECTRTC WELDING- CGBTPANY, 0F BOSTON, MASSACHUSETTS, A

CORPORATION 033 MASSACHUSETTS.

TRANSFORMER-SECONDARY CUNNECTION FOR ELECTRIC METAL-WORKING- APPARATUS.

Specification of Letters Patent.

Patented Apr. 26, 1921.

Application filed July 30, 1920. Serial No. 400,277.

To all 10 from it may concern:

My present invention relates to the method of and means for electrically connecting the transformer secondary of an electric metal working apparatus to the work-holders whereby the current induced in the secondary is conducted to the workends of the strips have been butted against thereto in this position.

'of the laminations and makes a localized Continued usage of the machine contact. causes the leads to loosen away from the plate, resulting in the current arcing across the joint and great loss of efficiency. In other cases the laminations have been bolted flat against a lug depending from the platen. In this case the current carried by the inner laminations must pass over and through each lamination and each joint between it and the work-holder or platen.

By. my invention an area of contact of any desired extent may be made with. the secondary and such contact is always main tained with each individual lamination. Again, by my invention the contact area is not localized at a certain place on the platen, thereby avoiding a localized heating, but is distributed :-,resulting in better radiation and cooling, as well as better distribution of the current for wide sections of work metal working apparatus as hereinafter more particularly described and then specifled in the claims.

In the accompanying drawings, Figure 1 is a cross-section through the transformer and the work-holder platens of an electric metal working apparatus organized in accordance with this invention.

I Fig. 2 is a side elevation of one of the secondary terminals or contact devices.

Fig. 3 is a transverse cross-section taken on the line 33 Fig. 1.

Referring to th drawings, 1, 1 indicates the platens of an electric metal working machine of any desired character for welding. brazing, heating, shaping or any other kind of operation for which this type of machines may be used.

2 indicates. the laminated secondary of an electric heating transformer of the type now generally used in electric metal working machines, the primary being indicated at 3 and the core at 4. The secondary is made up of a great number of thin laminatcd strips bundled together at each end by means of plates 9 and rivets or bolts 10.

. At each end ofv the secondary is located a contact device orterminaliconsisting of a pair of plates or arms 5, 5 preferably joined together by an integral yoke 16 (Fig. These plates engage the side edges of each of the laminations of the secondary 2 and may make such contact therewith for any desirable distance along the edges.

The contact plates 5, 5 are firmly clamped to the secondary by clamping plates 6, 6' secured together by bolts 7. To compensate for any relative difference in expansion of the individual laminations of the secondary due to the heating thereof resulting from the use of the machine, I preferably provide a double tapered surface on the clamping plates 6, 6' as indicated at 8, Fig. 3. if desired, the clamping plates 6, 6 may be dispensed with by having the bolts 7 act on the plates 5, 5 direct.

The yoke 6 which connects the contact plates 5, 5 terminates in a part 11 preferably integral therewith and of considerable width and which seats on the upper surface of the platen 1, 1 and is securely clamped thereto by screws 12. Work-holder blocks 13 are mounted on the part 11 in any suitable manner. .The character of the workholders varies, as is well known, according to the class of work being operated on and such work-holders and the general manner of operating machines of this character be ing now so well understood in the art, it is thought further illustration of this part of the apparatus is unnecessary.

The side edges of the laminations of the secondary as well as the surfaces of the contact plates are preferably machined or otherwise provided with finished edges and surfaces at the place of *ontact between the plates 5, 5 and the laminations so that a uniform, perfect, contact is attained.

The ends of the secondary are insulated from the platens 1, 1 preferably by insulation 1% and if desired a fastening screw 15 may be employed to mechanically secure the secondar direct to the platen. The fastening 15 is also preferably insulated from the platen so that no direct electrical connection is made between the end of the secondary and the platen.

In the operation, the current flows from each lamination of the secondary and at each side through the finished surfaces of the contact plates 5, 5, reducing the resistance to the flow of current, reducing the heat losses and reducing the I R drop in the circuit. The current being evenly distributed along the work-holder parts 13 makes the work more uniform.

Vhat I claim as my invention is 1. In an electric metal working apparatus, a transformer secondary of laminated strips bundled together at each nd, a contact plate engaging the side edges of each of the strips and means electrically connecting said plate with a work-holder.

2. In an electric metal working apparatus, a transformer secondary of laminated strips bundled together at their ends, a contact device secured to each end of the secondary, said Contact device engaging the side edges of each laminated strip and means electrically connecting said device with a workholder.

3. In an electric metal working apparatus, a transformer secondary of laminated strips bundled together at each end, contact plates engaging the opposite side edges of each lamination and means clamping said leads between said plates, said plates being electrically connected with a work-holder.

4. In an electric metal working apparatus, a transformer secondary of laminated strips bundled together at each end, contact plates at each end of the secondary forming terminals and clamped to and engaging opposite side edges of each lamination, insulation between the secondary leads and the workholder platens and means electrically connecting the contact plates with the workholders.

5. In an electric metal working apparatus,

the combination with the work-holder platens an i ork-holders carried thereby, of a transformer secondary of laminated strips bundled together each end and insulated from direct electrical contact with said platens, a contac device at each end of the secondary gripping the laminations therebetween and means electrically connecting said contact device to the work-holder at the gap of then .chine.

G. In an electric metal working apparatus, a transforme secondary of laminated strips bundled together at each end, contact plates clamped to the opposite side edges of said laminations and compensating means to allow for varia is in expansion of said laminations and maintain the contact between the laminations and said plates.

7. In an electric metal working apparatus, a transformer secondary of laminated strips bundled together at each end, contact plates applied to the opposite side edges of said laminations and clamping said plates in contact with the side edges of each lamination, said clamping means being adapted to maintain said plates in contact with each lamination under variation in expansion of said laminations.

8. The method of electrically connecting laminated transformer leads to the workholders of an electric metal working apparatus, consistino' in applying a contact plate to the sides of the leads and in contact therewith along the side edges of each lamination and electrically connecting said plate with the work-holder.

9. The method of electrically connecting laminated transformer leads to the workholders of an electric metal working apparatus, consisting in bundling the laminations together between contact plates making contact with each lamination along the side edges thereof and electrically connecting said plates to the work-holder.

10. The method of electrically connecting laminated transformer leads to the workholders of an electric metal working apparatus, consisting in bundling the laminations together in a contact device engaging each lamination along the side edges and electrically connecting said contact device with the work-holder.

11. The method of electrically connecting laminated transformer leads" to the workholders of an electric metal working apparatus, consisting in nsulating the leads from direct contact with the work-holder platens, bundling the leads together in a device making contact with each lead along the side edges thereof and electrically connectingsaid device to the work-holder.

Signed at Lynn, in the county of Essex and State of Massachusetts, this 21st day of July, A. D. 1920.

HERBERT ADDISON WOOFTER. 

